1. Field of the Invention
This invention relates to connecting a main casing section to a lateral casing section in a well, and more particularly, to an apparatus and method using a thermoset plastic molding in the form of a sock seal at the intersection of the casing sections.
2. Description of the Prior Art
Many oil and gas wells today include a laterally extending portion which extends away from a substantially vertical main portion of the well. These lateral sections, also sometimes referred to as horizontal sections or deviated sections, are used to intersect formations or zones of interest that cannot easily be accessed by merely a vertical well.
After a vertical portion of the well and a lateral portion have been drilled, casing is placed in both. At the intersection or joint of the main or vertical section of casing with the lateral section of casing, it is necessary to provide sealing so that proper well operations may be carried out and well fluids flowed out of the well without leakage in or out of the well casing.
Sealing at the joint or intersection presents problems, solutions to which have been proposed through the years. For example, sealing can be successfully achieved by using cements or other similar materials. However, a problem exists in keeping such a seal intact. Any slight earth movements, or pipe movements due to contraction or expansion in the casing may sever such seals. In these instances, the cement will crack, breaking the seal, and allowing leakage into or out of the casing joint, neither of which is desirable.
The present invention solves this problem by providing a flexible sock made of a hardenable material which can be placed at the joint so that the legs of the sock extend into the main casing section and the lateral casing section. The sock is inflated to an operating position and the material hardened. In this way, a single piece, uninterrupted seal is formed. Even with some casing or earth movement, the integrity of the one-piece seal is not broken.
The present invention includes an apparatus for sealing a connection between a main casing section and a lateral casing section in a well. The apparatus comprises a housing adapted for attachment to a tubing string and a sock having an upper end attached to the housing. The sock also has a first leg and a second leg and is made of a hardenable material. The apparatus may further comprise a bent sub connected to the housing and extending through the second leg of the sock. The housing, sock and bent sub may be positioned in the well adjacent to an intersection of the main and lateral casing sections, the sock may be inflated and placed in an operating position in which the first leg of the sock extends into the main casing section beyond the intersection and the second leg extends into the lateral casing section beyond the intersection, and the sock may be hardened in the operating position.
In one embodiment, the first leg of the sock has a closed end. The housing and the upper end of the sock are sealingly engaged, and the bent sub and the second leg of the sock are also sealingly engaged.
The sock is preferably made of a thermoset plastic material, and the apparatus may thus further comprise heating means for applying heat to the sock and thereby hardening the sock in the operating position. The heating means may comprise a heater connected to the housing and/or may comprise chemicals disposed in a cavity defined in the housing for providing an exothermic reaction when released from the cavity. The apparatus may thus comprise a rupture disc in communication with the cavity such that the rupture disc may be ruptured by applying pressure thereto, thereby releasing the chemicals from the cavity.
The invention may also be described as including a method of connecting and sealing between a main casing section and a lateral casing section in a well. The method comprises the steps of (a) positioning a flexible sock made of a hardenable material adjacent to an intersection of the main and lateral casing portions, the sock comprising a first leg and a second leg, (b) placing the sock in an operating position wherein the first leg of the sock is in contact with an inner surface of the main casing section, and the second leg of the sock is in contact with an inner surface of the lateral casing section, and (c) curing the hardenable material such that the sock is hardened in the operating position. Step (b) may comprise inflating the sock. Steps (b) and (c) may be substantially simultaneous.
Step (c) may comprise applying heat to the hardenable material. This step of heating may comprise releasing a volume of chemicals adjacent to the sock such that an exothermic reaction is generated and/or activating a heater positioned adjacent to the sock. The step of releasing the chemicals may comprise rupturing a rupture disc retaining the chemicals in a cavity defined in a housing positioned inside the sock.